U.S. patent number 5,405,896 [Application Number 08/163,556] was granted by the patent office on 1995-04-11 for adhesive silicone rubber compositions.
This patent grant is currently assigned to Shin-Etsu Chemical Co., Ltd.. Invention is credited to Hironao Fujiki, Akira Matsuda, Shigeki Shudo.
United States Patent |
5,405,896 |
Fujiki , et al. |
April 11, 1995 |
Adhesive silicone rubber compositions
Abstract
An adhesive silicone rubber composition of addition reaction
curing type comprising (a) an organopolysiloxane containing an
alkenyl group; (b) an organohydrogenpolysiloxane having at least
one hydrogen atom directly attached to a silicon atom in a
molecule; (c) an addition reaction catalyst; and (d) an adhesive
agent selected from compounds of the following formulae (I), (II)
and (III): wherein each of A and B is a silane or siloxane group,
each group having at least one hydrogen atom directly attached to a
silicon atom and an optional substituent which is a substituted or
unsubstituted monovalent hydrocarbon group having 1 to 8 carbon
atoms attached to the same or different silicon atom, A being
monovalent and B being divalent, each of C and D is a group having
contained therein at least one member selected from the group
consisting of a substituted or unsubstituted aryl group, a
substituted or unsubstituted arylene group, ##STR1## and an
optional substituent which is selected from alkyl or alkylene
groups, C being monovalent and D being divalent, E is a monovalent
group as defined for C, with the proviso that the total number of
atoms in E other than hydrogen and halogen atoms is at least 8, and
letter x is 0 or a positive number, said adhesive silicone rubber
composition giving a cured product that does not adhere to
metal.
Inventors: |
Fujiki; Hironao (Takasaki,
JP), Shudo; Shigeki (Annaka, JP), Matsuda;
Akira (Annaka, JP) |
Assignee: |
Shin-Etsu Chemical Co., Ltd.
(Tokyo, JP)
|
Family
ID: |
18425701 |
Appl.
No.: |
08/163,556 |
Filed: |
December 9, 1993 |
Foreign Application Priority Data
|
|
|
|
|
Dec 10, 1992 [JP] |
|
|
4-352679 |
|
Current U.S.
Class: |
524/265; 528/15;
528/31; 528/32; 525/474; 525/464; 525/446; 525/431; 525/106;
525/105; 525/100; 524/862; 524/730; 524/268; 524/731; 525/393 |
Current CPC
Class: |
C07F
7/0896 (20130101); C07F 7/21 (20130101); C08K
5/5419 (20130101); C08L 83/04 (20130101); C08K
5/5419 (20130101); C08L 83/04 (20130101); C08L
83/04 (20130101); C08L 83/00 (20130101); C08L
83/04 (20130101); C08L 83/00 (20130101); C08G
77/12 (20130101); C08G 77/20 (20130101); C08G
77/70 (20130101); C08L 2666/44 (20130101) |
Current International
Class: |
C08K
5/00 (20060101); C08L 83/00 (20060101); C08L
83/04 (20060101); C08K 5/5419 (20060101); C07F
7/00 (20060101); C07F 7/08 (20060101); C07F
7/21 (20060101); C08K 005/24 (); C08F 008/00 ();
C08L 083/00 (); C08G 077/06 () |
Field of
Search: |
;524/730,731,265,268,862
;525/100,105,106,393,431,446,464,474 ;528/15,31,32 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Marquis; Melvyn I.
Assistant Examiner: Dean; Karen A.
Attorney, Agent or Firm: Birch, Stewart, Kolasch &
Birch
Claims
We claim:
1. An adhesive silicone rubber composition of addition reaction
curing type comprising (a) an organopolysiloxane containing an
alkenyl group; (b) an organohydrogenpolysiloxane having at least
two hydrogen atoms directly attached to a silicon atom in a
molecule; (c) an addition reaction catalyst; and (d) an adhesive
agent selected from compounds of the following formulae (I), (II)
and (III):
wherein each of A and B is a silane or siloxane group, each group
having at least one hydrogen atom directly attached to a silicon
atom and an optional substituent which is a substituted or
unsubstituted monovalent hydrocarbon group having 1 to 8 carbon
atoms attached to the same or different silicon atom, A being
monovalent and B being divalent,
each of C and D is a group having contained therein at least one
member selected from the group consisting of a substituted or
unsubstituted aryl group, a substituted or unsubstituted arylene
group, ##STR14## and an optional substituent which is selected from
alkyl or alkylene groups, C being monovalent and D being
divalent,
E is a monovalent group as defined for C, with the proviso that the
total number of atoms in E other than hydrogen and halogen atoms is
at least 8, and
letter x is 0 or a positive number,
said adhesive silicone rubber composition giving a cured product
that does not adhere to metal.
2. The adhesive silicone rubber composition of claim 1, wherein
said at least one member contained in the groups represented by C,
D and E is selected from the following formulae (1) to (10):
##STR15## wherein each of R.sup.1 to R.sup.9, which may be
identical or different, is a monovalent group selected from the
group consisting of a hydrogen atom, halogen atom, hydroxyl group,
substituted or unsubstituted monovalent hydrocarbon group, and
alkoxy groups;
X is a divalent group selected from the group consisting of
##STR16## wherein each of R.sup.10 and R.sup.11, which may be
identical or different, is a monovalent group selected from the
group consisting of a hydrogen atom, halogen atom, and substituted
or unsubstituted monovalent hydrocarbon group, or R.sup.10 and
R.sup.11 taken together form a carbocyclic or heterocyclic ring,
and letter "a" is an integer of at least 2.
3. The composition of claim 1 or 2 wherein said compound has a
contact angle of up to 70.degree. on an organic resin to which the
composition is to be joined.
4. The adhesive silicone rubber composition according to claim 1,
wherein the adhesive agent is at least one compound selected from
the group consisting of ##STR17##
5. The adhesive rubber composition according to claim 1, wherein
the amount of the adhesive agent in the adhesive silicone rubber
composition is from 0.01 to 50 parts by weight per 100 parts by
weight of the organopolysiloxane containing an alkenyl group.
6. The adhesive silicone rubber composition according to claim 1,
wherein the amount of the adhesive agent in the adhesive silicone
rubber composition is from 0.1 to 5 parts weight per 100 parts by
weight of the organopolysiloxane containing an alkenyl group.
7. The adhesive silicone rubber composition according to claim 1,
wherein the organopolysiloxane containing an alkenyl group is
represented by the formula
wherein R is an substituted or unsubstituted monovalent hydrocarbon
group, letter a is a number from 1.9 to 2.4, and the content of
alkenyl group is from 0.01 to 10 mol % of the entire R groups.
8. The adhesive silicone rubber composition according to claim 7,
wherein the content of alkenyl group is from 0.1 to 1 mol % of the
entire R groups.
9. The adhesive silicone rubber composition according to claim 1,
wherein the organopolysiloxane containing an alkenyl group is
selected from the group consisting of ##STR18## wherein R is a
substituted or unsubstituted monovalent hydrocarbon group,
excluding an aliphatic unsaturated group, and letters m and n are
positive numbers and m+n=100 to 5000 and m/(m+n)=0.001 to 0.1.
10. The adhesive silicone rubber composition according to claim 1,
wherein the amount of the organohydrogenpolysiloxane in the
adhesive silicone rubber composition is from 0.4 to 5 equivalents
per alkenyl group in the organopolysiloxane containing an alkenyl
group.
11. The adhesive silicone rubber composition according to claim 1,
wherein the amount of the organohydrogenpolysiloxane in the
adhesive silicone rubber composition is from 0.8 to 2 equivalents
per alkenyl group in the organopolysiloxane containing an alkenyl
group.
12. The adhesive silicone rubber composition according to claim 1,
wherein the addition reaction catalyst is platinum, a platinum
compound, rhodium, or a rhodium compound.
13. The adhesive silicone rubber composition according to claim 12,
wherein the amount of the addition reaction catalyst in the
adhesive silicone rubber composition is from 0.1 to 1000 ppm of
platinum or rhodium based on the total composition.
14. The adhesive silicone rubber composition according to claim 12,
wherein the amount of the addition reaction catalyst in the
adhesive silicone rubber composition is from 1 to 200 ppm of
platinum or rhodium based on the total composition.
15. The adhesive silicone rubber composition according to claim 1,
wherein the adhesive agent is ##STR19##
16. The adhesive silicone rubber composition according to claim 1,
wherein the adhesive agent is ##STR20##
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to adhesive silicone rubber compositions
which adhere well to organic resins, and more particularly, to
silicone rubber compositions which adhere well to organic resins,
but not to metals.
2. Prior Art
A number of methods have been proposed for providing a bond between
addition curing type silicone rubber and organic resins. It is
known, for example, to form a bond by applying a primer to a
surface of molded resin, applying an uncured silicone rubber
material thereto and curing the silicone rubber to the resin or by
curing self-adhesive silicone rubber compositions directly to
molded resin. For the self-adhesive silicone rubber compositions, a
number of proposals have been made on their adhesive agent.
As another approach, it is known from Japanese Patent Publication
(JP-B) No. 34311/1990 to add an organohydrogenpolysiloxane
containing at least 30 mol % of hydrogen atoms directly attached to
silicon atoms to an organic resin so that the resin is bondable
with addition curing type silicone rubber. JP-B 45292/1988
discloses integration by physically fitting silicone rubber within
a molded organic resin. In Japanese Patent Application Kokai (JP-A)
No. 183843/1988, a compound having an aliphatic unsaturated group
and a hydrolyzable group attached to a silicon atom is grafted to
an olefin resin and silicone rubber is bonded and integrated with
the grafted olefin resin. Furthermore, as we previously proposed, a
thermoplastic resin can be bonded and integrated to a silicone
rubber composition when a compound having an unsaturated group and
a hydrogen atom directly attached to a silicon atom is added to the
resin (U.S. Ser. No. 07/965,303, now U.S. Pat. No. 5,366,806 and EP
0540259 A1).
However, several problems arise with these prior art methods for
integrating silicone rubber and organic resin into a one-piece
article. The primer method is cumbersome in that a molded resin
shape must be taken out of the mold before the primer can be
applied thereto. The method of applying and curing a self-adhesive
silicone rubber composition to molded resin has the serious problem
that if the resin and silicone rubber are molded into a one-piece
member using a mold, the silicone rubber itself adheres to the
mold.
Little problem occurs when silicone rubber is coated and cured on
resin preforms. However, for several of many general-purpose
resins, for example, ABS, PPO, PPS, polycarbonate, acryl, PE, PP
and Teflon, self-adhesive silicone rubber compositions of the
addition curing type cannot provide a sufficient bond to allow
utilization as one-piece articles.
When organohydrogenpolysiloxane is added to olefin resin, the
properties of the resin itself can be altered thereby, preventing
the resin from exerting its own properties. The physical engagement
method leaves a possibility that the two segments will be
disengaged by physical forces. When an olefin resin having grafted
thereto a compound having an aliphatic unsaturated group and a
hydrolyzable group attached to a silicon atom, a primer is
required, when the olefin resin is to be joined to an addition
curing type silicone rubber.
To take advantage of the weatherability, heat resistance,
cleanliness and rubbery elasticity of silicone rubber, the demand
that organic resin and silicone rubber be integrally molded into a
one-piece article under curing conditions within a short time is
increasing. There is a desire to have a silicone rubber composition
capable of forming an effective bond to organic resins.
SUMMARY OF THE INVENTION
Therefore, an object of the present invention is to provide a novel
and improved silicone rubber composition which can form a
satisfactory bond to organic resins, especially thermoplastic
resins under curing conditions within a short time and which
itself, after curing, can be released from a metallic silicone
rubber molding jig, typically a metallic mold, in a practically
acceptable manner.
We have found that when a compound of formula (I), (II) or (III)
defined below is blended in an adhesive silicone rubber composition
of addition reaction curing type as an adhesive agent, the
resulting silicone rubber composition can form a practically
acceptable bond to organic resins, especially thermoplastic resins,
but not to metals.
The adhesive silicone rubber composition of addition reaction
curing type according to the present invention includes at least
one member selected from compounds of the following general
formulae (I), (II) and (III).
Each of A and B is a silane or siloxane group, each group having at
least one hydrogen atom directly attached to a silicon atom and an
optional substituent which is a substituted or unsubstituted
monovalent hydrocarbon group having 1 to 8 carbon atoms attached to
a silicon atom, A being monovalent and B being divalent,
each of C and D is a group having contained therein at least one
member selected from the group consisting of a substituted or
unsubstituted arylene group, ##STR2## and an optional substituent
which is selected from alkyl or alkylene groups, C being monovalent
and D being divalent,
E is a monovalent group as defined for C, with the proviso that the
total number of atoms in E other than hydrogen and halogen atoms is
at least 8,
letter x is 0 or a positive number.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGS. 1A and 1B are side and plan views of an adhesion test
piece.
DETAILED DESCRIPTION OF THE INVENTION
The present invention pertains to an adhesive silicone rubber
composition of addition reaction curing type which includes at
least one member selected from compounds of formulae (I), (II) and
(III) as an adhesive agent.
The adhesive agent forms the essential part of the present
invention. The minimum requirement for this component is that the
compound contains at least one hydrogen atom directly attached to a
silicon atom in a molecule and improves affinity to an organic
resin to which the silicone rubber is to be joined. From the
standpoint of joining silicone rubber to organic resin, it is
preferred that the compound contains more than one hydrogen atom
directly attached to a silicon atom in a molecule.
This, however, is not enough to establish a good adhesion to
organic resins and it is additionally required that the adhesive
agent be compatible with the organic resin to which silicone rubber
is to be joined (to be referred to as adhered resin). From the
standpoint of reactivity with the organic resin, the bond is
significantly affected by a contact angle. The constituents
contained in the adhesive agent depend on the adhered resin. Many
adherend organic resins are generally composed of carbon, oxygen,
nitrogen and sulfur atoms. To enhance affinity to such organic
resins, the adhesive agent according to the invention should have a
group as represented by C, D and E, in addition to a silane or
siloxane group as represented by A and B.
More particularly, the adhesive agent is preferably in molten state
under actual joining conditions and in that state, the compound
should have a contact angle of up to 70.degree. on the adhered
organic resin (to which silicone rubber is to be joined) in order
to effectively attain the objects of the invention. Measurement of
the contact angle is generally at room temperature (25.degree. C.),
most preferably at the temperature during curing of the silicone
rubber. If the adhesive agent component is solid or waxy at room
temperature, it becomes necessary to measure the contact angle in
molten state.
In order that those skilled in the art will more readily understand
the concept of the adhesive agent according to the present
invention, the concept intended herein is described below by way of
illustration and not by way of limitation. We have found that (1)
an effective factor contributing to adhesion to thermoplastic
resins, that is, a major factor for the cohesive force developed
between cured silicone rubber and thermoplastic resin is a
hydrosilyl group (.tbd.SiH). Although it is not certainly
determined whether the hydrosilyl group undergoes hydrosilylation
with the resin or undergoes hydrolysis to form a silanol
(.tbd.SiOH) which acts as a secondary cohesive force for the bond,
the hydrosilyl group (.tbd.SiH) greatly contributes to the bond.
(2) Another important factor for adhesion is interaction with the
thermoplastic resin. It is presumed that the fact that the adhesive
agent includes a certain portion (a group as represented by C, D
and E) having a molecular moiety compatible with the adhered resin,
that is a thermoplastic resin will allow the adhesive agent to
approach the thermoplastic resin close enough to generate a
cohesive force therewith. This is the reason why the adhesive agent
as defined herein is not included in the organohydrogenpolysiloxane
which is conventionally used in addition reaction curing type
silicone rubber compositions as a curing agent. More particularly,
the organohydrogenpolysiloxane conventionally used as the curing
agent is a compound having low surface tension, as is well known in
the art, so that its contact angle with the resin surface is less
than 70.degree., but it fails to exert adhesiveness as contemplated
herein. This suggests that a group providing affinity to the
organic resin is necessary in addition to the siloxane agent. More
particularly, it is our understanding that in the structure of the
adhesive according to the invention, the hydrosilyl group plays the
role of a functional group exerting a cohesive force to the resin,
and the groups of C, D and E other than the siloxane group plays
the role of permitting the adhesive agent to approach toward the
resin within a zone where a cohesive force to the resin is
possible. To this end, the relevant portion should preferably have
an analogous structure to the particular organic resin to which the
silicone rubber is to be joined. The contact angle is one factor
indicative of the analogous structure.
Where the adhesive agent contains a nitrogen atom, its molecule
will be increased in polarity due to the nitrogen atom. In
practice, such adhesive agent is not acceptable as the adhesive
agent according to the invention because it is not only very
effective in providing adhesion to resins, but also promotes
adhesion to metals. Also simply for the purpose of providing
adhesion to resins, many conventional well-known adhesive agent
will be effective. Such typical adhesive agents are compounds
having both a hydrogen atom directly attached to a silicon atom and
at least one member of an alkoxysilyl, glycidyl and acid anhydride
group in a molecule. These compounds are effective for adhesion to
certain types of thermoplastic resins. It has been found that by
introducing an unsaturated group into an adhered organic resin for
modification or simple addition in mixed state, the bond between
the (modified) resin and the silicone rubber (containing the
tackifier component) is enhanced in a reliable manner. However,
these adhesive agents have the drawback in that they also provide
sufficient adhesion to metals as opposed to the subject matter of
the present invention.
Therefore, in order to avoid adhesion to metallic molds, the
adhesive agent used in the present invention should preferably be
selected from the compounds which are free of adhesive functional
groups as exemplified above, for example, trialkoxysilyl, glycidyl
and acid anhydride groups. It is to be noted that compounds having
such a functional group can be used without problem insofar as the
functional group is fully suppressed in reactivity by the steric
restraint or electronic action of a substituent group or neighbor
group.
As understood from the above discussion, the adhesive agent should
be selected from the compounds of formulae (I), (II) and (III)
having a group of A or B having at least one, preferably at least
two SiH groups and a group of C, D or E in a molecule.
Each of the linkages represented by C, D and E should preferably
contain therein at least one group selected from the following
formulae (1) to (10). ##STR3##
Each of R.sup.1 to R.sup.9, which may be identical or different, is
a monovalent group selected from the group consisting of a hydrogen
atom, halogen atom, hydroxyl group, substituted or unsubstituted
monovalent hydrocarbon group having 1 to 8 carbon atoms, and alkoxy
group having 1 to 6 carbon atoms;
X is a divalent group selected from the group consisting of
##STR4## wherein each of R.sup.10 and R.sup.11, which may be
identical or different, is a monovalent group selected from the
group consisting of a hydrogen atom, halogen atom, and substituted
or unsubstituted monovalent hydrocarbon group having 1 to 8 carbon
atoms, or R.sup.10 and R.sup.11 taken together form a carbocyclic
or heterocyclic ring, and letter a is an integer of at least 2.
Examples of the monovalent hydrocarbon group represented by R.sup.1
to R.sup.11 are the same as will be later described for R. Examples
of the carbocyclic and heterocyclic rings formed by R.sup.10 and
R.sup.11 taken together are given below. ##STR5##
Exemplary compounds included in the tackifier component are given
below. ##STR6##
The amount of the adhesive agent blended in a silicone rubber
composition is properly determined without undue experimentation,
although about 0.01 to 50 parts by weight, more preferably about
0.1 to 5 parts by weight per 100 parts by weight of an alkenyl
group-bearing organopolysiloxane, which will be later described as
component (a), is preferred. Less than 0.01 part of the adhesive
agent is too small to provide adherence to the adhered organic
resin, whereas more than 50 parts of the adhesive agent would
deteriorate the physical properties of silicone rubber and rather
promote adhesion to metals.
The adhesive silicone rubber composition of the invention is an
addition reaction curing type silicone rubber composition
containing the adhesive agent as an essential component. In
addition to the adhesive agent, the composition may contain
conventional components which are commonly used in conventional
silicone rubber compositions.
In addition to the adhesive agent, the adhesive silicone rubber
composition of the invention generally includes (a) an alkenyl
group-containing organopolysiloxane, (b) an
organohydrogenpolysiloxane, and (c) an addition reaction
catalyst.
Component (a) is an organopolysiloxane containing an alkenyl group
which may be selected from well-known organopolysiloxanes
conventionally used as a major component of addition reaction
curing type silicone rubber compositions, typically having a
viscosity of about 100 to 100,000 centipoise at room
temperature.
Preferred organopolysiloxanes are represented by the general
formula: R.sub.a SiO.sub.(4-a)/2 wherein R is a substituted or
unsubstituted monovalent hydrocarbon group, preferably having 1 to
8 carbon atoms. Examples of the hydrocarbon group represented by R
include alkyl groups such as methyl, ethyl and propyl; alkenyl
groups such as vinyl, propenyl and butenyl; aryl groups such as
phenyl and xylyl; and halo- or cyano-substituted hydrocarbon groups
such as 3,3,3-trifluoropropyl. The monovalent hydrocarbon groups
may be identical or different as long as an alkenyl group is
contained in the organopolysiloxane molecule. The content of
alkenyl group is preferably 0.01 to 10 mol %, especially 0.1 to 1
mol % of the entire R groups. Letter a is a number of 1.9 to 2.4.
The organopolysiloxane may be a linear one or a branched one
further containing a RSiO.sub.3/2 unit or SiO.sub.4/2 unit. The
substituent on the silicon atom is basically any of the
above-mentioned groups. It is desirable to introduce a vinyl group
among the alkenyl groups and a methyl or phenyl group among other
substituent groups.
Illustrative, non-limiting examples of the organopolysiloxane are
given below. ##STR7##
In these formulae, R is as defined above (excluding an aliphatic
unsaturated group), and letters m and n are positive numbers
meeting m+n=100 to 5000 and m/(m+n)=0.001 to 0.1.
The organopolysiloxanes may be prepared by per se known methods.
For example, they are obtained by effecting equilibration reaction
between an organocyclopolysiloxane and a hexaorganodisiloxane in
the presence of an alkali or acid catalyst.
Component (b) is an organohydrogenpolysiloxane which is used as a
curing agent in conventional addition reaction curing type silicone
rubber compositions. The organohydrogenpolysiloxane (b) serves as a
cross-linking agent by reacting with component (a). It is not
particularly limited in molecular structure and may be any of
conventionally used organohydrogenpolysiloxanes of linear, cyclic
and branched structures. However, it should have at least two
hydrogen atoms each directly attached to a silicon atom in a
molecule. The substituent or substituents attached to a silicon
atom other than hydrogen are the same as the substitutents
described for organopolysiloxane (a).
Component (b) is preferably added in an amount to provide 0.4 to 5
equivalents, especially 0.8 to 2 equivalents per alkenyl group in
component (a). Less than 0.4 equivalents of component (b) on this
basis would result in cured silicone rubber having too low
crosslinking density and hence, less heat resistance. More than 5
equivalents of component (b) would give rise to a bubbling problem
due to a dehydrogenation reaction, which would also adversely
affect heat resistance.
The organohydrogenpolysiloxanes may be prepared by per se known
methods. For example, the most commonly used method is by
equilibrating octamethylcyclotetrasiloxane and/or
tetramethylcyclotetrasiloxane and a compound containing a
hexamethyldisiloxane or 1,1-dihydro-2,2,3,3-tetramethyldisiloxane
unit, which will become a terminal group in the presence of a
catalyst such as sulfuric acid, trifluoromethanesulfonic acid, and
methanesulfonic acid, at a temperature between -10.degree. C. and
+40.degree. C.
Component (c) is an addition reaction catalyst which is generally
selected from platinum, platinum compounds, rhodium and rhodium
compounds. Since the catalyst is used for promoting curing addition
reaction or hydrosilation between components (a) and (b), it may be
a conventional known one. Exemplary are platinum black,
chloroplatinic acid, alcohol modified chloroplatinic acid,
complexes of chloroplatinic acid with olefins, aldehydes,
vinylsiloxanes or acetylene alcohols, and rhodium complexes. The
amount of the catalyst added is suitably determined in accordance
with a desired curing rate although it is generally in the range of
0.1 to 1000 ppm, preferably 1 to 200 ppm of platinum or rhodium
based on the total of the entire components.
In one preferred embodiment where the silicone rubber should have
physical strength, the silicone rubber composition further includes
finely divided silica having a specific surface area of at least 50
m.sup.2 /g in an amount of 0 to 100 parts, preferably 5 to 50
parts, more preferably 10 to 40 parts by weight per 100 parts by
weight of the total of components (a) and (b). Exemplary of
hydrophilic silica are Aerosil 130, 200 and 300 (commercially
available from Nippon Aerosil K.K. and Degussa), Cabosil MS-5 and
MS-7 (Cabot Corp.), Rheorosil QS-102 and 103 (Tokuyama Soda K.K.),
and Nipsil LP (Nippon Silica K.K.). Exemplary of hydrophobic silica
are Aerosil R-812, R-812S, R-972 and R-974 (Degussa), Rheorosil
MT-10 (Tokuyama Soda K.K.), and Nipsil SS series (Nippon Silica
K.K.).
In some cases, the curing time of the silicone rubber composition
must be controlled in order that it be effective in practice. Then
a suitable control agent is used. It may be selected from
vinyl-containing organopolysiloxanes such as
vinylcyclotetrasiloxane, triallylisocyanurate, alkyl maleates,
acetylene alcohols and silane or siloxane modified derivatives
thereof, hydroperoxides, tetramethylethylenediamine, benzotriazole
and mixtures thereof. Also useful are platinum group compounds
combined with organic resins and silicone resins.
Moreover, suitable additives may be blended in the silicone rubber
composition. Such additives include non-reinforcing fillers such as
ground quartz, diatomaceous earth, calcium carbonate, coloring
agents including inorganic pigments such as Cobalt Blue and organic
dyes, agents for improving heat resistance and flame retardance
such as cerium oxide, zinc carbonate, manganese carbonate, iron
oxide, titanium oxide, and carbon black.
The composition of the invention is advantageously used to join
with organic resins, especially thermoplastic resins to form
one-piece articles. Examples of the thermoplastic resin to which
the composition can be joined include polypropylene, polyethylene,
ABS resins, nylon, polycarbonate, polyphenylene oxide, polybutylene
terephthalate, polyphenylene sulfide, polyethylene terephthalate,
acrylic resins, polyacetal resins, and other engineering plastics
such as polyarylates, polysulfones, polyether sulfones, polyether
imides, polyether ether ketones, polyimides, and liquid crystal
polymers.
As long as a suitable adhesive agent is selected in accordance with
a particular adhered thermoplastic resin by considering its
wettability to the resin, there is obtained a silicone rubber
composition which adheres well to the thermoplastic resin, although
the adhesive agent is free of a functional group except for a
hydrogen atom directly attached to a silicon atom. That is, the
adhesive agent according to the present invention permits the
silicone rubber composition to exert selective adhesion to organic
resins to which conventional silicone rubber compositions were
regarded impossible to join firmly, while suppressing adhesion to
metals, typically metallic molds.
The thermoplastic resin to which the silicone rubber composition is
to be joined may take various shapes in common solid state,
although resin materials loaded with glass fiber reinforcements,
silica reinforcements and other inorganic reinforcements are
advantageous to form a more reliable adhesion. The glass fibers may
be those commonly used in resin reinforcement. The silica
reinforcements include crystalline and amorphous silica powders.
Other inorganic reinforcements include metal fibers such as brass
fibers, nickel fibers, stainless steel fibers, and aluminum fibers
as well as mica, talc, clay, kaolin, aluminum hydroxide, silicon
carbide whiskers, calcium sulfate, and calcium carbonate.
Better adhesion is achieved when such fillers have been treated
with substances having an unsaturated group such as
vinyl-containing silazanes, siloxasilazanes, vinylalkoxysilanes,
and vinyl-containing silicone resins. For improving adhesion to a
thermoplastic resin, it is also effective to introduce into or add
to the thermoplastic resin a component having an unsaturated group.
In introducing into or adding to the adhered thermoplastic resin a
component having an unsaturated group, it is necessary that the
unsaturated group be present at the time of adhesion. Little of
such benefit is observed when a compound having an aliphatic
unsaturated group and a hydrolysable group attached to a silicon
atom is grafted to an olefinic resin so that the unsaturated group
is substantially consumed as disclosed in JP-A 183843/1988.
Examples of the adhered thermoplastic resin which is modified by
introducing or adding a compound having an unsaturated group
include polycarbonate resins terminally modified with an aliphatic
unsaturated group such as a vinyl, allyl or methacryl group;
polyethylene and polypropylene modified with an aliphatic
unsaturated group at a side chain as disclosed in JP-A 269110/1990;
acrylic resins modified with an allyl ester group or vinyl dimethyl
silyl group at a side chain; and polyamide resins having an
aliphatic unsaturated group substituted on a nitrogen atom. Also
useful are dispersions in various resins of unsaturated
group-containing compounds such as triallyl isocyanurate, triallyl
trimellitate, unsaturated group-containing polybutadiene oligomers,
oligomers of unsaturated group-containing compounds, and
unsaturated group-containing silicone resins or polymers.
There have been described adhesive silicone rubber compositions
which provide improved adhesion to organic resins, but minimum
adhesion to metals so that they may be used in producing composite
articles of integrated silicone rubber and organic resins using
molds.
EXAMPLE
Examples of the present invention are given below by way of
illustration and not by way of limitation. All parts are by
weight.
Examples 1-4
Preparation of Silicone Rubber Composition
A kneader was charged with 100 parts of a dimethylsiloxane polymer
blocked with a dimethylvinylsilyl group at either end and having a
viscosity of 10,000 centipoise at 25.degree. C., 40 parts of fumed
silica having a specific surface area of 300 cm.sup.2 /g, 8 parts
of hexamethyldisilazane, and 1 part of water. The contents were
agitated and mixed at room temperature for one hour, heated to
150.degree. C., and mixed for a further 2 hours at the temperature.
Thereafter, the mixture was cooled down to room temperature. To the
mixture were added 20 parts of the dimethylsiloxane polymer blocked
with a dimethylvinylsilyl group at either end and having a
viscosity of 10,000 centipoise at 25.degree. C., 3 parts of a
methylhydrogenpolysiloxane represented by formula (i) below and
having a viscosity of about 10 centipoise at 25.degree. C., 4 parts
of a vinylmethylpolysiloxane containing 5 mol % of a vinyl group
directly attached to a silicon atom and having a viscosity of 1,000
centipoise at 25.degree. C., 0.1 part of acetylene alcohol for
extending the curing time at room temperature, and 50 ppm
calculated as platinum atom of a platinum vinylsiloxane complex.
The mixture was fully mixed until uniform, obtaining a liquid
addition type silicone rubber composition (S). ##STR8##
Composition (S) was pressed into a sheet at 120.degree. C. for 10
minutes. Upon measurement of mechanical properties, the sheet had a
hardness of 40 on JIS A scale, an elongation of 500%, a tensile
strength of 100 kgf/cm.sup.2, and a tear strength of 35 kgf/cm.
To 100 parts of silicone rubber composition (S) was added 0.5 or 1
part of a compound of formula (ii) or (iii) shown below as the
adhesive agent. There were obtained four silicone rubber
compositions within the scope of the invention. ##STR9##
Using these four silicone rubber compositions, the following tests
were carried out.
Test 1
A polyether ether ketone resin (PEEK) was admitted into a
thermoplastic resin injection molding machine where the resin was
plasticized at 360.degree. C. and injected into a plurality of
sheet-shaped mold cavities whereby a plurality of sheets of 25 mm
wide, 100 mm long, and 2 mm thick were molded. The injection
molding conditions included an injection time of 15 seconds, a
cooling time of 10 seconds, an injection pressure of 1,200
kg/cm.sup.2, a clamping pressure of 35 ton, and a cavity
temperature of 140.degree. C.
A polyether sulfone resin (PES) was similarly admitted into the
injection molding machine. A plurality of sheets of the same
dimensions were molded. The molding conditions included a
plasticizing temperature of 340.degree. C., an injection time of 10
seconds, a cooling time of 30 seconds, an injection pressure of
1,250 kg/cm.sup.2, a clamping pressure of 35 ton, and a cavity
temperature of 140.degree. C.
A polyether imide resin (PEI) was similarly admitted into the
injection molding machine. A plurality of sheets of the same
dimensions were molded. The molding conditions included a
plasticizing temperature of 360.degree. C., an injection time of 15
seconds, a cooling time of 30 seconds, an injection pressure of
1,000 kg/cm.sup.2, a clamping pressure of 35 ton, and a cavity
temperature of 90.degree. C.
To a jig for forming shear adhesion test pieces was fixedly
attached each of the resin sheets or each of chromium-plated metal,
nickel-plated metal and aluminum alloy sheets of the same
dimensions. A proper amount of the silicone rubber composition was
poured into the jig where it was cured by heating for 8 minutes in
a 120.degree. C. constant temperature oven, obtaining a test piece
as shown in the side and plan views of FIGS. 1A and 1B. In FIG. 1,
a resin or metal sheet 1 is joined to a cured part of the silicone
composition 2 (25.times.100.times.2 mm) through a bond zone 3.
Supports 4 and 5 support the resin or metal sheet 1 and the cured
silicone part 2, respectively. The test pieces were examined by an
adhesion test. The results are shown in Table 1.
Using an automatic contact angle meter (manufactured by Kyowa
Kaimen Kagaku K.K.), the adhesive agents (ii) and (iii) were
measured for contact angle on the polyether ether ketone, polyether
sulfon and polyether imide resin sheets. The results are shown in
Table 2.
TABLE 1 ______________________________________ Example 1 2 3 4
______________________________________ Adhesive agent (ii) 0.5 pbw
1 pbw -- -- Adhesive agent (iii) -- -- 0.5 pbw 1 pbw Adhered
Cr-plated metal peeled peeled peeled peeled Ni-plated metal peeled
peeled peeled peeled Al alloy peeled peeled peeled peeled PEEK
bonded bonded bonded bonded PES bonded bonded bonded bonded PEI
bonded bonded bonded bonded
______________________________________
TABLE 2 ______________________________________ Contact angle
(.theta.) Adhesive Agent (ii) Adhesive Agent (iii)
______________________________________ PEEK 48.0.degree.
28.7.degree. PES 49.1.degree. 30.1.degree. PEI 48.2.degree.
30.5.degree. ______________________________________
Test 2
A terminally allyl-modified polycarbonate resin (PC) was admitted
into a thermoplastic resin injection molding machine where the
resin was plasticized at 290.degree. C. and injected into a
plurality of sheet-shaped mold cavities whereby a plurality of
sheets of 25 mm wide, 100 mm long, and 2 mm thick were molded. The
injection molding conditions included an injection time of 6
seconds, a cooling time of 30 seconds, an injection pressure of
1,000 kg/cm.sup.2, a clamping pressure of 35 ton, and a cavity
temperature of 100.degree. C.
To a jig for forming shear adhesion test pieces was fixedly
attached the resin sheet or each of chromium-plated metal,
nickel-plated metal and aluminum alloy sheets of the same
dimensions. A proper amount of the silicone rubber composition was
poured into the jig where it was cured by heating for 8 minutes in
a 120.degree. C. constant temperature oven, obtaining a test piece
as shown in FIG. 1. The test pieces were examined by an adhesion
test. The results are shown in Table 3.
Using the automatic contact angle meter used in Test 1, the
adhesive agents (ii) and (iii) were measured for contact angle on
the polycarbonate resin sheet. The results are shown in Table
4.
TABLE 3 ______________________________________ Example 1 2 3 4
______________________________________ Adhesive agent (ii) 0.5 pbw
1 pbw -- -- Adhesive agent (iii) -- -- 0.5 pbw 1 pbw Adhered
Cr-plated metal peeled peeled peeled peeled Ni-plated metal peeled
peeled peeled peeled Al alloy peeled peeled peeled peeled modified
PC bonded bonded bonded bonded
______________________________________
TABLE 4 ______________________________________ Contact angle
(.theta.) Adhesive Agent (ii) Adhesive Agent (iii)
______________________________________ modified PC 35.9.degree.
10.0.degree. ______________________________________
Test 3
A polybutyrene terephthalate resin (PBT) loaded with 30% by weight
of glass fibers was admitted into a thermoplastic resin injection
molding machine where the resin was plasticized at 240.degree. C.
and injected into a plurality of sheet-shaped mold cavities whereby
a plurality of sheets of 25 mm wide, 100 mm long, and 2 mm thick
were molded. The injection molding conditions included an injection
time of 15 seconds, a cooling time of 10 seconds, an injection
pressure of 75 kg/cm.sup.2, a clamping pressure of 35 ton, and a
cavity temperature of 60.degree. C.
A polycarbonate resin (PC) loaded with 10% by weight of glass
fibers was similarly admitted into the injection molding machine. A
plurality of sheets of the same dimensions were molded. The molding
conditions included a plasticizing temperature of 290.degree. C.,
an injection time of 10 seconds, a cooling time of 30 seconds, an
injection pressure of 1,000 kg/cm.sup.2, a clamping pressure of 35
ton, and a cavity temperature of 100.degree. C.
An acrylonitrile-butadiene-styrene resin (ABS) loaded with 15% by
weight of glass fibers was similarly admitted into the injection
molding machine. A plurality of sheets of the same dimensions were
molded. The molding conditions included a plasticizing temperature
of 220.degree. C., an injection time of 15 seconds, a cooling time
of 30 seconds, an injection pressure of 800 kg/cm.sup.2, a clamping
pressure of 35 ton, and a cavity temperature of 50.degree. C.
To a jig for forming shear adhesion test pieces was fixedly
attached each of the resin sheets or each of chromium-plated metal,
nickel-plated metal and aluminum alloy sheets of the same
dimensions. A proper amount of the silicone rubber composition was
poured into the jig where it was cured by heating for 8 minutes in
a 120.degree. C. constant temperature oven, obtaining a test piece
as shown in FIG. 1. The test pieces were examined by an adhesion
test. The results are shown in Table 5.
Using automatic contact angle meter in Test 1, adhesive agents
components (ii) and (iii) were measured for contact angle on the
glass fiber-reinforced polybutyrene terephthalate, polycarbonate
and ABS resin sheets. The results are shown in Table 6.
TABLE 5 ______________________________________ Example 1 2 3 4
______________________________________ Adhesive agent (ii) 0.5 pbw
1 pbw -- -- Adhesive agent (iii) -- -- 0.5 pbw 1 pbw Adhered
Cr-plated metal peeled peeled peeled peeled Ni-plated metal peeled
peeled peeled peeled Al alloy peeled peeled peeled peeled
reinforced PBT bonded bonded bonded bonded reinforced PC bonded
bonded bonded bonded reinforced ABS bonded bonded bonded bonded
______________________________________
TABLE 6 ______________________________________ Contact angle
(.theta.) Adhesive Agent (ii) Adhesive Agent (iii)
______________________________________ reinforced PBT 40.3.degree.
18.70 reinforced PC 39.1.degree. 20.1.degree. reinforced ABS
38.3.degree. 20.5.degree.
______________________________________
Test 4
To 100 parts of unreinforced polycarbonate resin was added 5 or 10
parts of silica treated with vinyl-containing silazane. Each
silica-loaded resin was kneaded in a kneader/extruder at
270.degree. C. for 10 minutes and extruded thereby into strands
which were pelletized by means of a rotary cuter.
The silica-loaded polycarbonate resin was admitted into a
thermoplastic resin injection molding machine where the resin was
plasticized at 290.degree. C. and injected into a plurality of
sheet-shaped mold cavities whereby a plurality of sheets of 25 mm
wide, 100 mm long, and 2 mm thick were molded. The injection
molding conditions included an injection time of 6 seconds, a
cooling time of 30 seconds, an injection pressure of 1,000
kg/cm.sup.2, a clamping pressure of 35 ton, and a cavity
temperature of 100.degree. C.
To a jig for forming shear adhesion test pieces was fixedly
attached the resin sheet or each of chromium-plated metal,
nickel-plated metal and aluminum alloy sheets of the same
dimensions. A proper amount of the silicone rubber composition was
poured into the jig where it was cured by heating for 8 minutes in
a 120.degree. C. constant temperature over, obtaining a test piece
as shown in FIG. 1. The test pieces were examined by an adhesion
test. The results are shown in Table 7.
Using the automatic contact angle meter in Test 1, adhesive agents
components (ii) and (iii) were measured for contact angle on the
silica-loaded polycarbonate resin sheets. The results are shown in
Table 8.
TABLE 7 ______________________________________ Example 1 2 3 4
______________________________________ Adhesive agent (ii) 0.5 pbw
1 pbw -- -- Adhesive agent (iii) -- -- 0.5 pbw 1 pbw Adhered
Cr-plated metal peeled peeled peeled peeled Ni-plated metal peeled
peeled peeled peeled Al alloy peeled peeled peeled peeled
Silica-loaded PC 5 pbw bonded bonded bonded bonded 10 pbw bonded
bonded bonded bonded ______________________________________
TABLE 8 ______________________________________ Contact angle
(.theta.) Adhesive Agent (ii) Adhesive Agent (iii)
______________________________________ 5 pbw 25.9.degree.
20.0.degree. silica-loaded PC 10 pbw 36.0.degree. 29.2.degree.
silica-loaded PC ______________________________________
Examples 5-6
To 100 parts of silicone rubber composition (S) in Examples 1-4 was
added 0.5 or 1 part of a compound of formula (iv) shown below as
the adhesive agent. There were obtained two silicone rubber
compositions within the scope of the invention. ##STR10##
Using these two silicone rubber compositions, the following tests
were carried out.
Test 5
A nylon-66 resin was admitted into a thermoplastic resin injection
molding machine where the resin was plasticized at 280.degree. C.
and injected into a plurality of sheet-shaped mold cavities whereby
a plurality of sheets of 25 mm wide, 100 mm long, and 2 mm thick
were molded. The injection molding conditions included an injection
time of 6 seconds, a cooling time of 20 seconds, an injection
pressure of 800 kg/cm.sup.2, a clamping pressure of 35 ton, and a
cavity temperature of 80.degree. C.
To a jig for forming shear adhesion test pieces was fixedly
attached the resin sheet or each of chromium-plated metal,
nickel-plated metal and aluminum alloy sheets of the same
dimensions. A proper amount of the silicone rubber composition was
poured into the jig where it was cured by heating for 8 minutes in
a 120.degree. C. constant temperature oven, obtaining a test piece
as shown in FIG. 1. The test pieces were examined by an adhesion
test. The results are shown in Table 9.
Using the automatic contact angle meter in Test 1, the adhesive
agent (iv) was measured for contact angle on the nylon-66 resin
sheets. The results are shown in Table 10.
TABLE 9 ______________________________________ Example 5 6
______________________________________ Adhesive agent (iv) 0.5 pbw
1 pbw Adhered Cr-plated metal peeled peeled Ni-plated metal peeled
peeled Al alloy peeled peeled Nylon-66 bonded bonded
______________________________________
TABLE 10 ______________________________________ Contact angle
(.theta.) Adhesive Agent (iv)
______________________________________ Nylon-66 25.0.degree.
______________________________________
Examples 7-12
To 100 parts of silicone rubber composition (S) in Examples 1-4 was
added 0.5 or 1 part of a compound of formula (v), (vi) or (vii)
shown below as the adhesive agent. There were obtained six silicone
rubber compositions within the scope of the invention.
##STR11##
Using these six silicone rubber compositions, the following tests
were carried out.
Test 6
A nylon-66 resin loaded with 30% by weight of glass fibers was
admitted into a thermoplastic resin injection molding machine where
the resin was plasticized at 270.degree. C. and injected into a
plurality of sheet-shaped mold cavities whereby a plurality of
sheets of 25 mm wide, 100 mm long, and 2 mm thick were molded. The
injection molding conditions included an injection time of 15
seconds, a cooling time of seconds, an injection pressure of 800
kg/cm.sup.2, a clamping pressure of 35 ton, and a cavity
temperature of 80.degree. C.
Similarly, a polyethylene terephthalate resin (PET) loaded with 30%
by weight of glass fibers was admitted into the injection molding
machine. A plurality of sheets of the same dimensions were molded.
The molding conditions included a plasticizing temperature of
270.degree. C., an injection time of 10 seconds, a cooling time of
30 seconds, an injection pressure of 600 kg/cm.sup.2, a clamping
pressure of 35 ton, and a cavity temperature of 100.degree. C.
Similarly, a polyphenylene oxide resin (PPO) loaded with 20% by
weight of glass fibers was admitted into the injection molding
machine. A plurality of sheets of the same dimensions were molded.
The molding conditions included a plasticizing temperature of
270.degree. C., an injection time of 10 seconds, a cooling time of
30 seconds, an injection pressure of 1,000 kg/cm.sup.2, a clamping
pressure of 35 ton, and a cavity temperature of 100.degree. C.
To a jig for forming shear adhesion test pieces was fixedly
attached each of the resin sheets or each of chromium-plated metal,
nickel-plated metal and aluminum alloy sheets of the same
dimensions. A proper amount of the silicone rubber composition was
poured into the jig where it was cured by heating for 8 minutes in
a 120.degree. C. constant temperature oven, obtaining a test piece
as shown in FIG. 1. The test pieces were examined by an adhesion
test. The results are shown in Table 11.
TABLE 11 ______________________________________ Example 7 8 9 10 11
10 ______________________________________ Adhesive 0.5 1 -- -- --
-- agent (v) Adhesive -- -- 0.5 1 -- -- agent (vi) Adhesive -- --
-- -- 0.5 1 agent (vii) Adhered Cr-plated peeled peeled peeled
peeled peeled peeled metal Ni-plated peeled peeled peeled peeled
peeled peeled metal Al alloy peeled peeled peeled peeled peeled
peeled Fiber- reinforced bonded bonded bonded bonded bonded bonded
nylon 66 Fiber- reinforced bonded bonded bonded bonded bonded
bonded PET Fiber- reinforced bonded bonded bonded bonded bonded
bonded PPO ______________________________________
Comparative Examples 1-2
To 100 parts of silicone rubber composition (S) in Examples 1-4 was
added 0.5 or 1 part of a compound of formula (viii) shown below.
There were obtained two silicone rubber compositions outside the
scope of the invention. ##STR12##
To a jig for forming shear adhesion test pieces was fixedly
attached each of the polyether ether ketone, polyether sulfone, and
polyether imide resin sheets prepared as in the foregoing Examples.
A proper amount of the silicone rubber composition was poured into
the jig where it was cured by heating for 8 minute in a 120.degree.
C. constant temperature oven, obtaining a test piece as shown in
FIG. 1. The test pieces were examined by an adhesion test to find
that the silicone rubber was readily peeled from each resin
sheet.
The compound (viii) had a contact angle of 75.0.degree.,
72.5.degree. and 78.0.degree. on the polyether ether ketone,
polyether sulfone, and polyether imide resin sheets,
respectively.
Comparative Example 3
To 100 parts of silicone rubber composition (S) in Examples 1-4 was
added 2 parts of a compound of formula (ix) or (x) shown below.
There were obtained two silicone rubber compositions outside the
scope of the invention. ##STR13##
A polypropylene resin modified with 1.5 mol % of a diene compound
as described in JP-A 269110/1990 was admitted into a thermoplastic
resin injection molding machine where the resin was plasticized at
200.degree. C. and injected into a plurality of sheet-shaped mold
cavities whereby a plurality of sheets of 25 mm wide, 100 mm long,
and 2 mm thick were molded. The injection molding conditions
included an injection time of 6 seconds, a cooling time of 30
seconds, an injection pressure of 1,000 kg/cm.sup.2, a clamping
pressure of 35 ton, and a cavity temperature of 60.degree. C.
To a jig for forming shear adhesion test pieces was fixedly
attached the resin sheet or each of chromium-plated metal,
nickel-plated metal and aluminum alloy sheets of the same
dimensions. A proper amount of the silicone rubber composition was
poured into the jig where it was cured by heating for 8 minutes in
a 120.degree. C. constant temperature oven, obtaining a test piece
as shown in FIG. 1. The test pieces were examined by an adhesion
test. The results are shown in Table 12.
Using the automatic contact angle meter in Test 1, the adhesive
agents (ix) and (x) were measured for contact angle on the modified
polypropylene resin sheet. The results are shown in Table 13.
TABLE 12 ______________________________________ Comparative Example
3 ______________________________________ Modified PP bonded
Cr-plated metal bonded Ni-plated metal bonded Aluminum alloy bonded
______________________________________
TABLE 13 ______________________________________ Contact angle
(.theta.) Adhesive Agent (ix) Adhesive Agent (x)
______________________________________ Modified 24.1.degree.
15.0.degree. ______________________________________
Although some preferred embodiments have been described, many
modifications and variations may be made thereto in the light of
the above teachings. It is therefore to be understood that within
the scope of the appended claims, the invention may be practiced
otherwise than as specifically described.
* * * * *